Error diffusion generally operates to place dots or other patterns of a set of tones in a manner that creates the appearance of a larger number of shades or tones for an image. A variety of techniques exist to reduce undesirable visual artifacts associated with error diffusion. For example, visual artifacts can be reduced by serpentine traversal, application of a larger number of fixed error term weights, threshold perturbation, and tone dependent changes to the error term weights.
Printing devices, such as laser printers, typically exhibit better image quality with larger dots that can be finely adjusted in size, thus favoring clustered and fixed type dot arrangements for error diffusion. However, fixed dot locations for copying devices may cause undesirable moiré patterns in the image, for example, when copying an image that itself was printed with fixed dot locations. Thus, a more random nature type error diffusion of smaller dots may be preferable in such applications. With the continued emergence of devices that combine printing and copying functionality, techniques and configurations are needed to generate error diffusion patterns in a manner that balances these considerations.